AeroNautical Posted November 22, 2013 Share Posted November 22, 2013 I'd say more, but you guys have keen eyes and brilliant intuition, so... ideas? (not the crack) Vehicle: 99 XJ 4.0 AW-4 Bad oil pump? Bearings? Link to comment Share on other sites More sharing options...
Pete M Posted November 22, 2013 Share Posted November 22, 2013 what oil filter are you using? Link to comment Share on other sites More sharing options...
jimoshel Posted November 22, 2013 Share Posted November 22, 2013 Remove the OP sending unit and screw in a real oil pressure gauge. Mechanical. Just a check. Link to comment Share on other sites More sharing options...
AeroNautical Posted November 22, 2013 Author Share Posted November 22, 2013 what oil filter are you using? All I know is it's the longer Purilator filter. (Not my vehicle) Remove the OP sending unit and screw in a real oil pressure gauge. Mechanical. Just a check. It only seems to get this low after leaving the highway and idling, but I'll give it a shot. Anybody rent them out? Link to comment Share on other sites More sharing options...
sinkrun Posted November 22, 2013 Share Posted November 22, 2013 Friends do not let friends buy fram oil filters. Change it. Link to comment Share on other sites More sharing options...
AeroNautical Posted November 22, 2013 Author Share Posted November 22, 2013 Friends do not let friends buy fram oil filters. Change it. That was my mistake, it's a Purilator. Last changed about 5k miles ago with last oil change. Link to comment Share on other sites More sharing options...
Keyav8r Posted November 22, 2013 Share Posted November 22, 2013 What does the pressure read at higher RPM? Ditto what Jim said. Could be the sending unit, or the gauge, or it could be worn bearing clearances and/or a weak oil pump. Link to comment Share on other sites More sharing options...
Eagle Posted November 23, 2013 Share Posted November 23, 2013 What does the pressure read at higher RPM? Ditto what Jim said. Could be the sending unit, or the gauge, or it could be worn bearing clearances and/or a weak oil pump. ^^^ :agree: The factory spec is 13 psi minimum at idle with the engine at normal operating temperature. What's the pressure at 50 MPH in high gear? So far the photo isn't showing a problem. Also, what weight oil? Link to comment Share on other sites More sharing options...
comanche1989 Posted November 23, 2013 Share Posted November 23, 2013 My 98 Cherokee had the same exact reading, swapped the sending unit with a mopar replacement, and its back to reading 35 psi at hot idle. Link to comment Share on other sites More sharing options...
jpnjim Posted November 23, 2013 Share Posted November 23, 2013 Every 4.0L I ever pulled the pan on had copper showing on the rod bearings, even the 80k mile one I was saving as a backup. Loose bearing clearances from wear = lower oil pressure With that much mileage, I wouldn't be afraid to use a slightly thicker oil. Link to comment Share on other sites More sharing options...
dasbulliwagen Posted November 23, 2013 Share Posted November 23, 2013 I recently found a deal on 10-11 gallons of SJ rated 15-40 diesel motor oil that I started using in my 2.5. I too agree that something heavier and with good zinc content would be good for you. Anything SL rated or earlier will have the needed zinc. I wouldnt be too worried about it either, With that many miles just keep running it and caring for it like normal till it tells you otherwise. Link to comment Share on other sites More sharing options...
dave92cherokee Posted November 23, 2013 Share Posted November 23, 2013 Friends do not let friends buy fram oil filters. Change it. That was my mistake, it's a Purilator. Last changed about 5k miles ago with last oil change. First thing to do is if it's been 5k change the oil, use a proper filter like wix or something that we all know as reliable. If it's been that long it could be simply low on oil or the oil has broken down causing it to not maintain the pressure as well. Link to comment Share on other sites More sharing options...
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